1. Field of the Invention
This invention relates to an electronic unit manufacturing apparatus and method for reflow soldering.
2. Description of the Related Art
A conventional electronic unit manufacturing apparatus and method will be discussed. As shown in FIG. 32, the conventional electronic unit manufacturing apparatus using the conventional electronic unit manufacturing method includes an adhesive printer 1 for printing an adhesive on a printed-circuit board, a chip placement machine 2 for placing chips on the printed-circuit board on which the adhesive is printed by the adhesive printer 1, a drier 3 for drying the printed-circuit board on which the chips are placed by the chip placement machine 2, and a deformed part insertion machine 4 for inserting deformed parts such as a coil, a capacitor, and an IFT transformer into the printed-circuit board dried by the drier 3. The printed-circuit board into which the deformed parts are inserted by the deformed part insertion machine 4 is inserted into a metal frame and frame assembling 5 is executed, then batch soldering is performed on a solder dip layer 6 to finish manufacturing the electronic unit. The reason why the conventional electronic unit manufacturing apparatus using the conventional electronic unit manufacturing method cannot accomplish reflow soldering with good soldering quality is that if non-heat-resistant parts easily affected by high temperature, such as an electrolytic capacitor and an IFT transformer, of the deformed parts inserted into the printed-circuit board are reflow-soldered at the same time as the chips, the parts are destroyed due to reflow heat.
However, for the adhesive printer 1 to print an adhesive on a printed-circuit board in the conventional manufacturing apparatus using the solder dip layer 6 to protect the non-heat-resistant parts, as shown in FIG. 33, if the amount of an adhesive 8a printed on a printed-circuit board 7 is small, a small bonding force is provided. Thus, a chip 9 may drop from the printed-circuit board 7 before dip-soldering is performed in the solder dip layer 6. If the adhesive amount is large, the adhesive squeezes out from the chip 9 as adhesive 8b. Resultantly, as shown in FIG. 34, solderability of solder 10 is poor and chips 9 may drop from the printed-circuit board 7. In soldering using the solder dip layer 6, inevitably a short circuit caused by a solder bride 11, a discontinuous part 12 not soldered, and the like occur as shown in FIG. 35; the worker must correct the defects by manual soldering in the later process.
It is therefore an object of the invention to provide an electronic unit manufacturing apparatus for protecting non-heat-resistant parts from high temperature and providing good soldering quality for lessening correction work.
To solve the above object, there is provided an electronic unit manufacturing apparatus includes: a cream solder printer for printing cream solder on one side of a printed-circuit board; a chip placement machine for placing a plane-mounted part on the printed-circuit board on which the cream solder is printed; a first reflow furnace for fixedly securing the plane-mounted part to the printed-circuit board; a solder application machine for applying a larger amount of cream solder than that printed by the cream solder printer in the vicinity of holes made in the one side of the printed-circuit board; and a second reflow furnace for inserting pins of a deformed part into the holes made in the printed-circuit board from an opposite side thereof and fixedly securing the pins of the deformed part to the printed-circuit board, wherein in the second reflow furnace. In the second reflow furnace, temperature on the opposite side of the printed-circuit board is set lower than temperature on the""one side thereof.
Thus, when the electronic unit is manufactured, the non-heat-resistant parts are protected from high temperature heat and good soldering quality is provided for drastically lessening correction work.